1. Field of the Invention
The present invention relates generally to a gas turbine combined cycle system and more particularly to a gas turbine combined cycle system in which heating of fuel and cooling of gas turbine moving blade and stationary blade cooling air are carried out by steam generated at a waste heat recovery boiler so as to enhance an efficiency.
2. Description of the Prior Art
FIG. 14 is a system diagram of a gas turbine combined cycle system in the prior art. In FIG. 14, the prior art combined cycle system is constructed by a gas turbine 8, a waste heat recovery boiler 9 and a steam turbine 29. In the gas turbine 8, suction air is taken into a compressor 2 to be compressed to a predetermined pressure and while the compressed air is partially used for cooling of gas turbine blades, the most part thereof is led into a combustor 3 to be mixed with fuel for generation of a high temperature gas. The high temperature gas enters a turbine 6 to expand for work and a turbine output after deduction of a compressor output generates an electric power at a generator 1.
While outlet air of the compressor 2 is partially used for blade cooling in the turbine 6, this air, having a high temperature, is cooled to a predetermined temperature at a blade cooling air cooler 4 using a cooling fan 5 and is then used for the turbine blade cooling. Thus, the air so led from the compressor 2 is once cooled at the blade cooling air cooler 4 using the cooling fan 5 to be then supplied into the turbine 6. By this cooling using the cooling fan 5, heat of the blade cooling air cooler 4 is discharged outside in vain and this has caused a reduction in the thermal efficiency of the gas turbine and the combined cycle system (gas turbine efficiency and combined efficiency). It is to be noted that the fuel is supplied into the combustor 3 without being preheated.
On the other hand, as for the waste heat recovery boiler 9, outlet steam of a low pressure turbine 23 is converted into water from steam at a condenser 25. Then, the water is pressurized at a feed water pump 26 and heated at a feed water heater 10 to become a saturated water. This saturated water is separated into three systems of water. The first one becomes a saturated steam at a low pressure evaporator 11 and becomes a superheated steam at a low pressure superheater 15 and is then supplied to an inlet of the low pressure turbine 23. The second one is pressurized to a predetermined pressure at an intermediate pressure pump 28, becomes a saturated water at an intermediate pressure economizer 12, becomes a saturated steam at an intermediate pressure evaporator 14 and becomes a superheated steam at an intermediate pressure superheater 16 and is then supplied to an inlet of a reheater 20.
And the third one is pressurized to a predetermined pressure at a high pressure pump 27, becomes a saturated water at a first high pressure economizer 13 and a second high pressure economizer 17, becomes a saturated steam at a high pressure evaporator 18 and becomes a superheated steam at a high pressure superheater 19 and is then led into a high pressure turbine 21. The mentioned superheated steam enters the high pressure turbine 21, the intermediate pressure turbine 22 and the low pressure turbine 23, respectively, to expand for generating an output and this output is converted into an electric power at a generator 24.
As mentioned above, in the prior art gas turbine combined cycle system, the fuel is supplied into the combustor without being preheated and the compressed air from the compressor is partially led into the blade cooling air cooler to be cooled and is then supplied for cooling of the gas turbine moving blades and stationary blades. Cooling of the combustor is also done by cooling air. The air for cooling the blades is once cooled at the blade cooling air cooler using the cooling fan and the heat obtained by the cooling is discharged outside in vain and this has caused a reduction in thermal efficiency of the gas turbine and the combined cycle system.
In view of the mentioned problem in the prior art, therefore, it is an object of the present invention to provide a gas turbine combined cycle system in which fuel to be supplied into a gas turbine combustor is preheated by steam taken from a waste heat recovery boiler, a combustor tail tube is cooled by the steam taken from the waste heat recovery boiler in place of air and gas turbine moving blades and stationary blades are also cooled by the steam taken from the waste heat recovery boiler and further the steam after used for cooling the combustor tail tube or the gas turbine moving blades and stationary blades is recovered to be recycled so that efficiency of the gas turbine and the combined cycle system may be enhanced.
In order to achieve the mentioned object, the present invention provides means of the following (1) to (13):
(1) A gas turbine combined cycle system comprising; a steam turbine having a high pressure turbine, an intermediate pressure turbine and a low pressure turbine; a condenser for condensing exhaust steam of the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling system for cooling the combustor and blades of the turbine; and a waste heat recovery boiler having components of a feed water heater, an intermediate pressure economizer, a low pressure superheater, an intermediate pressure superheater, a high pressure superheater, a high pressure evaporator and a reheater and being fed with exhaust gas of the gas turbine so that condensed water coming from the condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively, characterized in that there is provided a fuel heater for heating the fuel before the fuel enters the combustor and saturated water coming from the intermediate pressure economizer of the waste heat recovery boiler is partially diverged to flow to the fuel heater for heating the fuel and the saturated water so used for heating the fuel is supplied to an inlet of the feed water heater.
(2) A gas turbine combined cycle system comprising; a steam turbine having a high pressure turbine, an intermediate pressure turbine and a low pressure turbine; a condenser for condensing exhaust steam of the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling system for cooling the combustor and blades of the turbine; and a waste heat recovery boiler having components of a feed water heater, an intermediate pressure economizer, a low pressure superheater, an intermediate pressure superheater, a high pressure superheater, a high pressure evaporator and a reheater and being fed with exhaust gas of the gas turbine so that condensed water coming from the condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively, characterized in that there is provided a fuel heater for heating the fuel before the fuel enters the combustor and saturated water coming from the intermediate pressure economizer of the waste heat recovery boiler is partially diverged to flow to the fuel heater for heating the fuel and the saturated water so used for heating the fuel is supplied to the condenser.
(3) A gas turbine combined cycle system as mentioned in (1) or (2) above, characterized in that the cooling system for cooling the combustor is fed with steam coming from the intermediate pressure superheater of the waste heat recovery boiler so as to cool a tail tube of the combustor and the steam heated by cooling the tail tube of the combustor is supplied to an inlet of the intermediate pressure turbine of the steam turbine.
(4) A gas turbine combined cycle system as mentioned in (1) or (2) above, characterized in that the cooling system for cooling the combustor is fed with steam coming from the intermediate pressure superheater of the waste heat recovery boiler so as to cool a tail tube of the combustor and the steam heated by cooling the tail tube of the combustor is supplied to an inlet side of the intermediate pressure turbine of the steam turbine and the cooling system for cooling the blades of the turbine is fed with steam coming from an outlet of the high pressure turbine of the steam turbine so as to cool the blades of the turbine and the steam heated by cooling stationary blades of the turbine is supplied to the inlet side of the intermediate pressure turbine of the steam turbine and the steam heated by cooling moving blades of the turbine is supplied to the reheater of the waste heat recovery boiler.
(5) A gas turbine combined cycle system as mentioned in (1) or (2) above, characterized in that the cooling system for cooling the combustor and the blades of the turbine is fed with steam coming from an outlet of the high pressure turbine of the steam turbine and the steam heated by cooling a tail tube of the combustor and the steam heated by cooling stationary blades of the turbine are supplied to an inlet side of the intermediate pressure turbine of the steam turbine and the steam heated by cooling moving blades of the turbine is supplied to the reheater of the waste heat recovery boiler and steam coming from the intermediate pressure superheater of the waste heat recovery boiler is mixed into an inlet of the cooling system for cooling the moving blades of the turbine.
(6) As gas turbine combined cycle system as mentioned in (1) or (2) above, characterized in that the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler.
(7) A gas turbine combined cycle system as mentioned in (3) above, characterized in that the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
(8) A gas turbine combined cycle system as mentioned in (4) above, characterized in that the cooling system for cooling the blades-of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
(9) A gas turbine combined cycle system as mentioned in (5) above, characterized in that the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
(10) A gas turbine combined cycle system as mentioned in (1) or (2) above, characterized in that there is provided an opening/closing valve in a system for leading the saturated water from the intermediate pressure economizer of the waste heat recovery boiler to the fuel heater and the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler.
(11) A gas turbine combined cycle system as mentioned in (3) above, characterized in that there is provided an opening/closing valve in a system for leading the saturated water from the intermediate pressure economizer of the waste heat recovery boiler to the fuel heater and the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
(12) A gas turbine combined cycle system as mentioned in (4) above, characterized in that there is provided an opening/closing valve in a system for leading the saturated water from the intermediate pressure economizer of the waste heat recovery boiler to the fuel heater and the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
(13) A gas turbine combined cycle system as mentioned in (5) above, characterized in that there is provided an opening/closing valve in a system for leading the saturated water from the intermediate pressure economizer of the waste heat recovery boiler to the fuel heater and the cooling system for cooling the blades of the turbine is supplied with a portion of water at an outlet of the feed water heater of the waste heat recovery boiler by a high pressure pump so that air of the cooling system may be cooled and the water heated by cooling the air is supplied into the high pressure evaporator of the waste heat recovery boiler and the air so cooled is supplied to the blades of the turbine.
According to the invention of (1) or (2) above, the saturated water heated at the intermediate pressure economizer is partially diverged to flow to the fuel heater for heat exchange with the fuel. Then, the saturated water is supplied to the inlet of the feed water heater in the invention (1) or to the condenser in the invention (2). The fuel is heated at the fuel heater and is supplied into the combustor. Thereby, the fuel flow rate becomes less and there is obtained an effect to enhance the combined efficiency.
According to the invention of (3) above, the tail tube of the combustor is cooled by the intermediate pressure superheater outlet steam and the heated steam is supplied to the inlet of the intermediate pressure turbine. Thereby, the combustion air used in the combustor increases in the quantity and the combustion temperature in the combustor is reduced as compared with the case of air cooling. Thus, generation of NOx is reduced. Also, like in the invention of (1) or (2) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case and the gas turbine efficiency and the combined efficiency can be enhanced.
According to the invention of (4) above, the stationary blades and the moving blades of the turbine are cooled by steam supplied from the outlet of the high pressure turbine. The steam heated by cooling the stationary blades is supplied to the inlet of the intermediate pressure turbine and the steam heated by cooling the moving blades is supplied to the middle portion of the reheater. Thereby, the cooling air which has been used for cooling the stationary blades and the moving blades is largely reduced in the quantity so that the combustion air may be increased and there is obtained an effect to enhance both the gas turbine output and efficiency, resulting in the enhancement both of the combined output and efficiency. Also, like in the invention of (3) above, the tail tube of the combustor is cooled by steam supplied from the intermediate pressure superheater and the steam heated by cooling the tail tube is supplied to the inlet of the intermediate pressure turbine and thereby the combustion temperature is reduced and generation of NOx is also reduced. Further, as the fuel is heated at the fuel heater, the fuel flow rate can be made less than in the conventional case.
According to the invention of (5) above, the tail tube of the combustor is cooled by a portion of the high pressure turbine outlet steam, not by the intermediate pressure superheater outlet steam, and the intermediate pressure superheater outlet steam is mixed into the inlet of the moving blade cooling steam so that the moving blade cooling steam supply temperature may be reduced. As the intermediate pressure superheater outlet temperature is lower than the high pressure turbine outlet temperature, the moving blade cooling steam supply temperature is reduced and cooling of the moving blades, which constitute an important rotational portion, can be strengthened. Also, like in the invention of (1) or (2) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case and the gas turbine efficiency and the combined efficiency can be enhanced.
According to the invention of (6) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (1) or (2) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case and the gas turbine efficiency and the combined efficiency can be enhanced.
According to the invention of (7) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased and the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (3) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case. Further, the tail tube of the combustor is cooled by the intermediate pressure superheater outlet steam and -the heated steam is supplied to the inlet of the intermediate pressure turbine. Thereby, the combustion air used in the combustor increases in the quantity and the combustion temperature in the combustor is reduced as compared with the case of air cooling. Thus, generation of NOx is reduced.
According to the invention of (8) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (4) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case. Further, the tail tube of the combustor is cooled by the intermediate pressure superheater outlet steam and the heated steam is supplied to the inlet of the intermediate pressure turbine. Thereby, the combustion air used in the combustor increases in the quantity and the combustion temperature in the combustor is reduced as compared with the case of air cooling. Thus, generation of NOx is reduced. Further, like in the invention of (4) above, the stationary blades and the moving blades of the turbine are cooled by steam supplied from the outlet of the high pressure turbine. The steam heated by cooling the stationary blades is supplied to the inlet of the intermediate pressure turbine and the steam heated by cooling the moving blades is supplied to the middle portion of the reheater. Thereby, the cooling air which has been used for cooling the stationary blades and the moving blades is largely reduced in the quantity so that the combustion air may be increased and there is obtained an effect to enhance both the gas turbine output and efficiency, resulting in the enhancement both of the combined output and efficiency.
According to the invention of (9) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (5) above, the fuel is heated at the fuel heater and thereby the fuel flow rate becomes less than in the conventional case and the gas turbine efficiency and the combined efficiency are enhanced. Further, the stationary blades and the moving blades-of the turbine are cooled by steam supplied from the outlet of the high pressure turbine. The steam heated by cooling the stationary blades is supplied to the inlet of the intermediate pressure turbine and the steam heated by cooling the moving blades is supplied to the middle portion of the reheater. Thereby, the cooling air which has been used for cooling the stationary blades and the moving blades is largely reduced in the quantity so that the combustion air may be increased and there is obtained an effect to enhance both the gas turbine output and efficiency, resulting in the enhancement both of the combined output and efficiency. Also, like in the invention of (5) above, the tail tube of the combustor is cooled by a portion of the high pressure turbine outlet steam, not by the intermediate pressure superheater outlet steam, and the intermediate pressure superheater outlet steam is mixed into the inlet of the moving blade cooling steam so that the moving blade cooling steam supply temperature may be reduced. As the intermediate pressure superheater outlet temperature is lower than the high pressure turbine outlet temperature, the moving blade cooling steam supply temperature is reduced and cooling of the moving blades, which constitute an important rotational portion, can be strengthened.
According to the invention of (10) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. If the fuel is of a high temperature without being preheated or if heating of the fuel is dangerous because of characteristics of the fuel, then the opening/closing valve is closed so that the construction may be made as if no fuel heater for preheating the fuel is provided.
According to the invention of (11) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. If the fuel is of a high temperature without being preheated or if heating of the fuel is dangerous because of characteristics of the fuel, then the opening/closing valve is closed so that the construction may be made as if no fuel heater for preheating the fuel is provided. Also, like in the invention of (3) above, the tail tube of the combustor is cooled by the intermediate pressure superheater outlet steam and the heated steam is supplied to the inlet of the intermediate pressure turbine. Thereby, the combustion air used in the combustor increases in the quantity and the combustion temperature in the combustor is reduced as compared with the case of air cooling. Thus, generation of NOx is reduced.
According to the invention of (12) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (4) above, the tail tube of the combustor is cooled by the intermediate pressure superheater outlet steam and the heated steam is supplied to the inlet of the intermediate pressure-turbine. Thereby, the combustion air used in the combustor increases in the quantity and the combustion temperature in the combustor is reduced as compared with the case of air cooling. Thus, generation of NOx is reduced. Further, the stationary blades and the moving blades of the turbine are cooled by steam supplied from the outlet of the high pressure turbine. The steam heated by cooling the stationary blades is supplied to the inlet of the intermediate pressure turbine and the steam heated by cooling the moving blades is supplied to the middle portion of the reheater. Thereby, the cooling air which has been used for cooling the stationary blades and the moving blades is largely reduced in the quantity so that the combustion air may be increased and there is obtained an effect to enhance both the gas turbine output and efficiency resulting in the enhancement both of the combined output and efficiency. If the fuel is of a high temperature without being preheated or if heating of the fuel is dangerous because of characteristics of the fuel, then the opening/closing valve is closed so that the construction may be made as if no fuel heater for preheating the fuel is provided.
According to the invention of (13) above, the high pressure pump outlet water is partially diverged to be heat-exchanged with the blade cooling air of the cooling system for cooling the blade cooling air. The water so heat-exchanged is heated and supplied into the high pressure evaporator. Thereby, while the waste heat of the cooling system for cooling the blade cooling air has been discharged outside in vain because of cooling by the cooling fan, this waste heat is made use of so that the high pressure generated steam of the waste heat recovery boiler may be increased in the quantity. Thus, the steam turbine output is increased and the combined efficiency and the combined output are enhanced. Also, like in the invention of (5) above, the stationary blades and the moving blades of the turbine are cooled by steam supplied from the outlet of the high pressure turbine. The steam heated by cooling the stationary blades is supplied to the inlet of the intermediate pressure turbine and the steam heated by cooling the moving blades is supplied to the middle portion of the reheater. Thereby, the cooling air which has been used for cooling the stationary blades and the moving blades is largely reduced in the quantity so that the combustion air may be increased and there is obtained an effect to enhance both the gas turbine output and efficiency, resulting in the enhancement both of the combined output and efficiency. Further, like in the invention of (5) above, the tail tube of the combustor is cooled by a portion of the high pressure turbine outlet steam, not by the intermediate pressure superheater outlet steam, and the intermediate pressure superheater outlet steam is mixed into the inlet of the moving blade cooling steam so that the moving blade cooling steam supply temperature may be reduced. As the intermediate pressure superheater outlet temperature is lower than the high pressure turbine outlet temperature, the moving blade cooling steam supply temperature is reduced and cooling of the moving blades, which constitute an important rotational portion, can be strengthened. If the fuel is of a high temperature without being preheated or if heating of the fuel is dangerous because of characteristics of the fuel, then the opening/closing valve is closed so that the construction may be made as if no fuel heater for preheating the fuel is provided.